do not allow zero window to be set
do not allow zero window to be set

erikdejonge/slowhttptest,shekyan/slowhttptest,blu3sh3ll/slowhttptest,rodrigoac/slowhttptest,blu3sh3ll/slowhttptest,rodrigoac/slowhttptest,drat/slowhttptest,michalkoczwara/slowhttptest,shekyan/slowhttptest,drat/slowhttptest,erikdejonge/slowhttptest,michalkoczwara/slowhttptest